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  • 1
    Electronic Resource
    Electronic Resource
    Coalescence of magnetic islands including anomalous resistivity (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3533-3543 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional compressible magnetohydrodynamic simulations of the coalescence instability in a low-beta plasma are presented in which anomalous resistivity is permitted to occur. The instability is considered in a uniform current sheet configuration, initially perturbed by an infinite chain of spots of anomalous resistivity. The two phases of the instability known from simulations based on the Fadeev equilibrium—ideal and resistive—can clearly be distinguished also in this configuration. It is found that the conversion of magnetic energy into kinetic energy dominates Ohmic heating. The main energy release occurs within a few Alfvén transit times. The scaling of several key parameters in the current layer formed between the coalescing islands is compared to the scalings obtained with uniform resistivity. The numerical results indicate that the peak reconnection rate decreases toward large Lundquist numbers (S(very-much-greater-than)104) as S−α with α=〈fraction SHAPE="CASE"〉15–〈fraction SHAPE="CASE"〉13 and that a transition to slow reconnection (α∼〈fraction SHAPE="CASE"〉12) may occur at S(approximately-greater-than)107, where S is based on the background resistivity. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872250
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic current sheets with localized anomalous resistivity (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 4703-4711 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional compressible magnetohydrodynamic simulations of current sheet dynamics under the influence of localized anomalous resistivity are presented. The system is initially perturbed by several spots of anomalous resistivity distributed in the sheet. Following a phase of induced tearing resulting from the initial perturbation, magnetic island coalescence occurs until one island persists. Finally the evolution becomes eruptive, dominated by the acceleration and ejection of a plasmoid, as a consequence of the amplification of a small initial asymmetry after a few 102 Alfvén times. These processes are accompanied by strong enhancements of the current density. It exceeds the threshold of kinetic instability repeatedly and leads to recurrence of anomalous resistivity, which drives the evolution. Jets are formed, driven by field line reconnection and locally enhanced dissipation at dominant X-points. The conversion of magnetic energy into kinetic energy is most efficient during the acceleration phase of the plasmoid. The evolution becomes more impulsive and leads to stronger current density enhancements for higher Lundquist numbers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872037
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  • 3
    Electronic Resource
    Electronic Resource
    Third plasma harmonic radiation in type II bursts (1992)
    Springer
    Solar physics 140 (1992), S. 149-160 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present observational evidence for simultaneous fundamental, second and third harmonic radio emission during an excessively strong type II burst on February 16, 1984. This burst was emitted from an active region behind the limb allowing for fair resolution of the wave bands. If interpreted as a triple harmonic system, three different, nearly equally probable mechanisms for higher harmonic emission are qualitatively discussed. These are a four-wave process which involves very strong Langmuir waves, a decay process first proposed by Cairns (1987) for higher harmonic emission near the Earth's bow shock, and time evolution of the emitted frequency during Langmuir wave collapse. In sufficiently strong coronal shock waves, both of the former mechanisms may be more efficient than under solar wind conditions. In the third mechanism, Langmuir wave collapse may be driven by strong electron beams as are expected to exist in quasiparallel shocks where electron reflection may be strongest. We discuss the differences between the signatures of these mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148435
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  • 4
    Electronic Resource
    Electronic Resource
    Fiber bursts in type IV dm radio continua as a signature of coronal current sheet dynamics (1992)
    Springer
    Solar physics 141 (1992), S. 371-379 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the late phase of some complex flare events which produce type IV radio emission, a narrow-band decimetric component with generally a high abundance of spectral fine structures is observed. We identify this late dm continuum as a hypothetical ‘switch-off’ signature of the equivalent two-ribbon flare current system. The quasi-periodic and highly dynamic fiber-burst pattern studied in the February 5, 1986 example is understood as radio evidence for a final reactivation of a cyclic sequence of instabilities in the driven reconnecting current sheet below the rising prominence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155186
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  • 5
    Electronic Resource
    Electronic Resource
    Microwave characteristics of a behind-the-limb proton flare (1991)
    Springer
    Solar physics 134 (1991), S. 171-186 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Behind-the-limb flares provide a unique opportunity for the study of vertical source structures of microwave bursts and dynamic flare processes. Based on complex observational data related to the outstanding solar proton event on 16 February, 1984, the development of burst emission at a height z ≥ 200000 km above the photosphere has been investigated. A comparison with the associated X-ray emission measured aboard various spacecraft yields a time lag of about ≤ 1 min between the onset of the unocculted impulsive HXR-emission and the onsets of the X-ray and microwave emissions occulted by the solar limb. The lag corresponds to a range of speeds of the propagation of the flare volume of about 3000–5000 km s−1. Considering competing transport agents that could account for such expansion of the source volume, a qualitative model of shock-wave activation of loops successively reaching into larger coronal heights is proposed. From a discussion of the possible emission processes involved, conclusions about the magnetic field, electron density, and particle energies have been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148746
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  • 6
    Electronic Resource
    Electronic Resource
    Electrostatic Wave Instability and Plasma Radiation from Coronal Loops (1997)
    Springer
    Solar physics 176 (1997), S. 147-152 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Polarization properties of solar and stellar radio emission require, in some cases, emission below the third or fourth coronal electron gyro level, ω 〈 3,ω_c; 4, ω_c. In the context of plasma radiation, the source parameters should be such that the ‘intermediate magnetic field condition’ 1 〈 ω p 2 /ω c 2 〈 3 is satisfied. Supposing this condition, we investigate the generation of electrostatic waves in a ‘warm’ background plasma with a high-energy component of magnetically trapped electrons. We invoke the conversion of upper-hybrid waves and Bernstein waves into electromagnetic radiation as being responsible for intense radio emission from a coronal magnetic loop. Moreover, ‘odd-half’ harmonic emissions in the solar radio spectrum as well as the o-mode polarization at the second harmonic of the plasma frequency are natural consequence of this proposed model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004949529063
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  • 7
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    3D Reconstruction of a Rotating Erupting Prominence (2011)
    Springer
    Details
    Publication Date: 2011-11-08
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 8
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    Fiber bursts in type IV dm radio continua as a signature of coronal current sheet dynamics (1992)
    Springer
    Details
    Publication Date: 1992-10-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 9
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    The birth of a coronal mass ejection (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉The Sun’s atmosphere is frequently disrupted by coronal mass ejections (CMEs), coupled with flares and energetic particles. The coupling is usually attributed to magnetic reconnection at a vertical current sheet connecting the flare and CME, with the latter embedding a helical magnetic structure known as flux rope. However, both the origin of flux ropes and their nascent paths toward eruption remain elusive. Here, we present an observation of how a stellar-sized CME bubble evolves continuously from plasmoids, mini flux ropes that are barely resolved, within half an hour. The eruption initiates when plasmoids springing from a vertical current sheet merge into a leading plasmoid, which rises at increasing speeds and expands impulsively into the CME bubble, producing hard x-ray bursts simultaneously. This observation illuminates a complete CME evolutionary path capable of accommodating a wide variety of plasma phenomena by bridging the gap between microscale and macroscale dynamics.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Ideal kink instability of a magnetic loop equilibrium (2004)
    EDP Sciences
    Details
    Publication Date: 2004-01-01
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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